Silver and Sunlight: The Science of Early Photography

Daguerreotype of the 1843 Nantes flood by an unknown photographer. Courtesy of Charles Isaacs Photographs, inc., New York.

Niépce soon acquired an unlikely collaborator. Louis-Jacques-Mandé Daguerre, born near Paris, was a theatrical artist and relentless self-promoter. In the 1820s he had devised the Diorama, a popular form of entertainment in which the scenery itself became the show. With clever lighting, large-scale backdrops painted on semitransparent gauze seemed to merge into each other, presenting a convincing illusion of day changing into night or of people moving through the scene. Familiar with the camera obscura from his work on these perspective paintings, Daguerre also dreamed of capturing the fleeting images within the box. Like some previous experimenters, he used silver chloride but didn’t have much to show for it. He often visited the Paris shop of Vincent and Charles Chevalier, father and son instrument makers and opticians, to examine new apparatus and lenses. Here, in 1826, he first learned of Niépce, whom the Chevaliers also supplied with optical instruments.

Ever the enthusiast, Daguerre wrote Niépce to ask how far his work had progressed, announcing that “for a long time, I, too, have been seeking the impossible.” Startled by this bold approach from a total stranger, Niépce remained wary for some time. In 1829, however, after prolonged negotiations, the two men entered into a partnership, agreeing to share any profits from the new invention once it had been perfected. Niépce supplied most of the knowledge; Daguerre provided energy and imagination. The two met only once but corresponded frequently, sharing research results. They were experimenting with silver-coated plates treated with iodine when Niépce died of a sudden stroke in July 1833 at age 69. Daguerre continued the work, painstakingly trying different lenses, chemicals, and processes to improve and fix the heliographic image.

From Niépce’s research Daguerre knew that exposure to light sometimes created a latent image: one that did not become visible until treated with more chemicals. Sometime in 1835 he discovered that mercury vapor made this latent image appear strongly on a copper plate coated with a thin silver layer, but it took him two more years to fix such images permanently with a salt solution. Despite its permanence, the resulting picture had drawbacks. It required a long exposure (several minutes or more), had a fragile surface (needing to be covered with glass and encased), lacked color, and was difficult to see except at certain angles. The image, however, had a remarkable richness of tone and was incredibly sharp and detailed. A magnifying glass revealed wonders that an artist’s pencil could never capture.

Photography Becomes Public

Daguerre, building on Niépce’s work, had finally created a practical picture-making technique, which he named after himself—much to the surprise of Niépce’s son and heir, Isidore. Daguerre planned to profit from the daguerreotype, but events soon took a different turn, thanks to an unusual man. François-Jean-Dominique Arago began his career as a geographical surveyor but then became involved in scientific studies of magnetism and light. Elected to the Académie des Sciences at the young age of 23, Arago brought his scientific interests into politics when in 1830 he became a member of France’s main legislative body, the Chambre des Députés.

When Daguerre approached a group of prominent scientists in late 1838, seeking subscribers for his invention, Arago quickly realized the potential of the new technique. Such an important innovation, he believed, should not remain in the hands of a few individuals. Instead, Arago planned to persuade the French government to buy the invention from Daguerre and Isidore Niépce, thus making it available to the world. He began his campaign with an announcement to the Académie des Sciences in January 1839, praising the “plates on which the [camera obscura] image is reproduced down to the most minute details with unbelievable exactitude and finesse.”